He's back in New Jersey where I grew up, but he's all on his own and I want to bring him out to Los Angeles so he's not lonely in his retirement years. 

LOTS of lakes that bring in out of state visitors and ski mountains galore.

In the grand scheme of things, yes, you should eventually replace the windows so 1) They operate properly. 2) It doesn't turn away potential tenants or cause maintenance hassles when a new one moves in.3) Tenants have proper egress in case of an emergency (like fire).Now, windows are expensive, so you'll have to decide how much you're willing to spend, based on how much income the property is bringing in.

And as mentioned in one of the other posts, when it was done 20 years ago it did not end well for a lot of people.  

I would strongly recommend attending one or two so you can start networking and meeting people in the industry.

Do something small on your own first, figure out what you are doing, and bring them in later when there are metrics to prove your concept.Also, side note on this - "will be bringing my girlfriend in who will be paying me rent in this home as I plan on living in one of the units and renting out the other/others (she will have no ownership and understands this she's not what my question is about.)" - this will ruin that relationship in seconds.

I am looking to connect with people who are doing out of state investing.

Based on the info I've received from a few nice people here, it's looking like a BRRRR/house hack is going to be my next best bet.

It's good you can bring some perspective to the starting line as you are a broker.I advise beginners all the time how to start and how to set expectations.You said you came into some money, you didn't say how much, so let's say it is 100k, if it is more great, you do not need more than 100k though to get started.I live in South Jersey, property taxes are high and home values are 400k+. 

Which will bring plenty of other investors and general business to the area.